1. Field of the Invention
The present invention relates to a device substrate attachment structure, and particularly to a device substrate attachment structure for electrical and electronic equipment or the like for which a countermeasure is provided to make it possible to attach a substrate to a substrate holding body including a frame made of sheet metal or the like without using attachment screws.
2. Description of the Related Art
FIG. 9 is a schematic perspective view showing a conventional example of a device substrate attachment structure. This example is a device substrate attachment structure for a liquid crystal television receiver, and a substrate 50 is attached to a frame 10 made of sheet metal that is provided on the back portion of a liquid crystal module. The frame 10 has, at a plurality of locations of the flat portion thereof, bulging parts 11 that are each formed into a substantially circular truncated cone shape. In contrast to this, terminals 61 such as jacks, other necessary electrical and electronic parts 62, and the like are mounted on the rectangular substrate 50. Furthermore, a terminal holder 60 that holds the terminals 61 is installed at an end portion of the substrate 50, and the substrate 50 and the terminal holder 60 are joined by a known fixing mechanism that is not illustrated. Then, the substrate 50 equipped with the terminal holder 60 is screw-fastened to the apex portions of the bulging parts 11 at a plurality of locations using attachment screws 12 in a state of being mounted over the bulging parts 11 of the frame 10.
In the device substrate attachment structure, between the substrate 50 and the frame 10, a gap is formed which corresponds to the height of the bulging parts 11. The gap serves as a space for preventing electrical shorts resulting from the sheet metal frame 10 being contacted by the circuit pattern, terminal pins, solder protrusions, or the like of the substrate 50. Moreover, the gap also serves as an accommodation space for electrical and electronic parts mounted on the back surface of the substrate 50. In addition, the gap is designed to reliably avoid the danger of shorts or the like by giving a certain margin for the depth of the gap. Furthermore, though not illustrated, the terminal holder 60 is also screw-fastened to the frame 10.
FIG. 10 is an explanatory diagram showing forbidden bands added to the substrate 50 that is fixed to the frame 10 by the screw fastening structure adopted in the conventional example of FIG. 9. A “forbidden band” is an area on a plate surface in which forming of a circuit pattern is forbidden, or an area on a plate surface in which mounting of a mounting space for electrical and electronic parts (including terminals) is forbidden. The substrate 50 shown in FIG. 10 is formed in a rectangular shape, and terminals 61 such as jacks are mounted in a line on each of the two end portions in the lengthwise direction of the substrate 50. When the substrate 50 is attached to the frame 10 by adopting the device substrate attachment structure according to the conventional example described with reference to FIG. 9, not only is it necessary to provide unavoidable forbidden bands Z1 at the locations indicated by the dotted-line cross hatching in this figure, i.e., between adjacent terminals 61 arranged in a line, but it is also necessary to provide forbidden bands Z2 at locations facing the other sites for screw fastening, specifically, the locations facing the bulging parts 11 provided on the frame 10 (see FIG. 9). Moreover, when the ratio of a total area of the forbidden bands Z1 and Z2 with respect to the entire area of the plate surface of the substrate 50 was calculated for certain specific models, this was found to be approximately 11.5%, and it became clear that ten percent or more of the space on the substrate 50 is occupied by the forbidden bands Z1 and Z2.
Meanwhile, proposed in a prior example is an invention that relates to a structure for attaching a circuit substrate used for liquid crystal display devices, plasma display devices, or the like to a support member (for example, see Japanese Patent Application Laid-Open Publication No. 2008-4801). The substrate attachment structure proposed in Japanese Patent Application Laid-Open Publication No. 2008-4801 combines the engagement of attachment claws provided on the side of the support member with parts to be attached of the circuit substrate, and screw fastening of the substrate to the support member at a plurality of locations.
In addition, proposed in another prior example is a power supply switch attachment structure for a thin liquid crystal display device (for example, Japanese Patent No. 4241805 corresponding to Japanese Patent Application Laid-Open Publication No. 2008-129369). It is indicated in Japanese Patent No. 4241805 that a jack holder provided at an end portion of a substrate is screw-fastened to the main substrate.
In contrast to each of these prior examples, prior examples adopting a structure that fixes a substrate without using attachment screws have also been proposed (for example, see Japanese Patent Application Laid-Open Publication No. 2009-181037). With the structure proposed in Japanese Patent Application Laid-Open Publication No. 2009-181037, in addition to a long and narrow substrate being laid across between a pair of left and right ribs provided integrally with the front cabinet of a display device, one end portion of the substrate in the lengthwise direction, the other end portion of which in the lengthwise direction is engaged with one of the ribs, is engaged with a hook-shaped rib.
However, with the conventional example adopting a screw fastening structure such as that shown in FIG. 9, as was described with reference to FIG. 10, there is a need to secure a space of ten percent or more of the plate surface of the substrate 50 as the forbidden bands Z1 and Z2, so the effective usable area of the substrate 50 ends up becoming correspondingly smaller. As a result, compared to the substrate 50 of the originally required size, there is no choice but to use a substrate 50 of a size that is larger to the extent that it corresponds to the area of the forbidden bands Z2 determined at locations facing the bulging parts 11 on the side of the frame 10 (see FIG. 9) of the forbidden bands Z1 and Z2, thus posing a problem in that this easily brings about an increase in the cost and size of the substrate installation space.
Furthermore, not only is there the trouble of having to perform screw fastening at several locations, but there is also the problem that, when the attachment screws 12 are repeatedly attached and detached with respect to the screw holes provided in the apex portions of the bulging parts 11 of the frame 10, these screw holes end up losing their function as such and becoming so-called “loose holes,” which makes it impossible to tighten the attachment screws 12 at these locations.
Meanwhile, with the example described in Japanese Patent Application Laid-Open Publication No. 2009-181037 which does not adopt a screw fastening structure, there is no way to encounter the trouble of having to perform screw fastening or to create the problem of having the screw holes end up becoming so-called “loose holes.” However, the locking structure proposed in Japanese Patent Application Laid-Open Publication No. 2009-181037 merely proposes a structure for having a long, narrow, flat substrate be bridged across a pair of left and right ribs formed as an integral unit with the front cabinet composed of a resin molded body. Therefore, as the substrate attachment structure such as the one having the terminal holder 60 attached to the end portion thereof as in the substrate shown in FIG. 9, when considering that the terminal holder 60 will become an obstacle, it is difficult to use this structure “as is” as a substrate attachment structure such as one having the terminal holder 60 attached thereto.